GB 2 312 930 A discloses an exhaust-gas turbocharger of the type in question with a turbine housing and a turbine arranged therein, wherein the turbine housing has two exhaust-gas channels which are separated from each other via a partition. Furthermore, a wastegate valve is provided via which the two exhaust-gas channels are connectable to a bypass duct bypassing the turbine.
DE 198 53 391 A1 discloses a wastegate valve for controlling the charge air pressure, in which some of the exhaust gas can be conducted via a bypass past a turbine into an exhaust-gas system. In order to avoid instabilities of the wastegate valve during opening and closing, the valve body is designed in such a manner that a progressively increasing cross section is obtained during the opening operation. For this purpose, the valve body is, for example, of hemispherical design.
US 2005/086936 A1 in turn discloses an exhaust-gas turbocharger with a turbine housing and a turbine arranged therein, wherein the turbine housing has two exhaust-gas channels which are separated from each other via a partition. A wastegate valve is likewise provided via which the two exhaust-gas channels can be connected to a bypass duct bypassing the turbine.
Generally, a differentiation is made in exhaust-gas turbochargers between what is referred to as ram supercharging and pulse supercharging, wherein, in the case of the ram supercharging, the pressure pulsations, which are caused by discharging, of the individual cylinders are smoothed in a single exhaust-gas collecting container. By this means, within the range of high motor rotational speeds, a turbine can put through more exhaust gas at a low pressure. Since it is possible for the motor to discharge counter to a lower exhaust-gas counter pressure, the fuel consumption is reduced in this operating range. However, the comparatively low motor torque at lower rotational speeds has a disadvantageous effect.
In order, at low motor rotational speeds to be able in turn to obtain a large motor torque, use is made of what is referred to as pulse supercharging. In this case, the exhaust gases of the individual cylinders are conducted in individual pipelines to the turbine of the exhaust-gas turbocharger. Owing to small pipe diameters, use is made of the kinetic energy of the exhaust-gas pulsation. The pressure in the lines is not constant here. The individual exhaust-gas lines are also guided separately here within the turbine housing as far as the turbine wheel, which can be achieved, for example, by means of a multi-channel housing.
The invention is therefore concerned with the problem of specifying, for an exhaust-gas turbocharger of the type in question, an improved or at least an alternative embodiment which overcomes disadvantages known from the prior art.
This problem is achieved according to the invention by the subject matter of the independent Claim(s). Advantageous embodiments are the subject matter of the dependent claims.